.\"	$OpenBSD: BN_CTX_new.3,v 1.4 2016/11/20 15:46:43 schwarze Exp $
.\"	OpenSSL aafbe1cc Jun 12 23:42:08 2013 +0100
.\"
.\" This file was written by Ulf Moeller <ulf@openssl.org>.
.\" Copyright (c) 2000, 2013 The OpenSSL Project.  All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\"
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\"
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in
.\"    the documentation and/or other materials provided with the
.\"    distribution.
.\"
.\" 3. All advertising materials mentioning features or use of this
.\"    software must display the following acknowledgment:
.\"    "This product includes software developed by the OpenSSL Project
.\"    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
.\"
.\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
.\"    endorse or promote products derived from this software without
.\"    prior written permission. For written permission, please contact
.\"    openssl-core@openssl.org.
.\"
.\" 5. Products derived from this software may not be called "OpenSSL"
.\"    nor may "OpenSSL" appear in their names without prior written
.\"    permission of the OpenSSL Project.
.\"
.\" 6. Redistributions of any form whatsoever must retain the following
.\"    acknowledgment:
.\"    "This product includes software developed by the OpenSSL Project
.\"    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
.\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
.\" PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
.\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
.\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
.\" OF THE POSSIBILITY OF SUCH DAMAGE.
.\"
.Dd $Mdocdate: November 20 2016 $
.Dt BN_CTX_NEW 3
.Os
.Sh NAME
.Nm BN_CTX_new ,
.Nm BN_CTX_free ,
.Nm BN_CTX_init
.Nd allocate and free BN_CTX structures
.Sh SYNOPSIS
.In openssl/bn.h
.Ft BN_CTX *
.Fo BN_CTX_new
.Fa void
.Fc
.Ft void
.Fo BN_CTX_free
.Fa "BN_CTX *c"
.Fc
.Pp
Deprecated:
.Pp
.Ft void
.Fo BN_CTX_init
.Fa "BN_CTX *c"
.Fc
.Sh DESCRIPTION
A
.Vt BN_CTX
is a structure that holds
.Vt BIGNUM
temporary variables used by library functions.
Since dynamic memory allocation to create
.Vt BIGNUM Ns s
is rather expensive when used in conjunction with repeated subroutine
calls, the
.Vt BN_CTX
structure is used.
.Pp
.Fn BN_CTX_new
allocates and initializes a
.Vt BN_CTX
structure.
.Pp
.Fn BN_CTX_free
frees the components of the
.Vt BN_CTX
and, if it was created by
.Fn BN_CTX_new ,
also the structure itself.
If
.Xr BN_CTX_start 3
has been used on the
.Vt BN_CTX ,
.Xr BN_CTX_end 3
must be called before the
.Vt BN_CTX
may be freed by
.Fn BN_CTX_free .
If
.Fa c
is a
.Dv NULL
pointer, no action occurs.
.Pp
.Fn BN_CTX_init
(deprecated) initializes an existing uninitialized
.Vt BN_CTX .
This should not be used for new programs.
Use
.Fn BN_CTX_new
instead.
.Sh RETURN VALUES
.Fn BN_CTX_new
returns a pointer to the
.Vt BN_CTX .
If the allocation fails, it returns
.Dv NULL
and sets an error code that can be obtained by
.Xr ERR_get_error 3 .
.Sh SEE ALSO
.Xr BN_add 3 ,
.Xr BN_CTX_start 3 ,
.Xr BN_new 3 ,
.Xr ERR_get_error 3
.Sh HISTORY
.Fn BN_CTX_new
and
.Fn BN_CTX_free
are available in all versions of SSLeay and OpenSSL.
.Fn BN_CTX_init
was added in SSLeay 0.9.1b.
